Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
cach thuc » anh thuc, cac thu
cac thuc » cac thu, can thuc, cay thuc
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
hieu ve » hieu van
dang ma » dang mau, dang mam, dang mat
ky dang » ky nang, ky danh
ma hoi » mai hoi, xa hoi, ma hoa
va dau » va dao
dau va » dau ve, lau va
va cua » va chua, via cua, ca cua
cua te » cua tu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuat sach ky dang ma hoi. ((hieu ve) or (hieu va)) ((cac thuc) OR (cach thuc)) va dau va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach ky dang ma hoi. ((hieu ve) OR (hieu va)) ((cac thuc) OR (cach thuc)) va dau va cua te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky dang ma hoi. ((hieu ve) or (hieu va)) ((cac thuc) OR (cach thuc)) va dau va cua te*".